fighting for obama care instead of fighting for jobs for the american people. >> we did work on this alongside working on jobs, because this is part of making sure that middle class families are secure in this country. >> reporter: president obama on defense, romney challenging his record, as both now wait to see if this exchange has any impact on voters. it had impact online. on twitter, the most tweeted event in u.s. political history. lynn? >> all right, tracie, thanks. well, post debate instant polls reveal that most voters believe mitt romney did better than president obama. a cnn orc poll finds that 67% of registered voters who watched the debate chose mr. romney as the winner while 25% picked mr. obama. a cbs news snap poll of uncommitted voters found that 46% identified mitt romney as the winner, while 22% said barack obama won. 32% declared the debate a tie. while the candidates tangled over taxes, bringing up countless statistics and figures of cuts or increases, nbc news' andrea mitchell looked into the truth behind the rhetoric of both candidates. >> let me repeat what i